Engineering Innovation for Ice Adhesion and Friction CONTROL
Last updated: September, 2011
Contact: Catharine Lamm
De-icing the world
Dartmouth Engineering Professor Victor Petrenko and his research team discovered that applying short pulses of electricity directly to an ice-material interface produces some novel and desirable effects. This discovery led them to invent an ultra-fast and efficient method of ice removal and prevention called pulse electro-thermal de-icing (PETD).
The heating effect of Petrenko's thin-film, PETD technology creates a melt-water layer with nearly perfect efficiency and, in the future, will be used to de-ice windshields, power lines, roofs, roads, walkways, runways, refrigerators, airplane wings, helicopter blades, and windmills, just to name a few.
Goodrich Corporation has acquired three licenses to use PETD technology in aviation, wind power generation, and for marine applications. Easy Ice, Inc. acquired a license to use PETD in commercial ice makers.
How does it work?
Petrenko's PETD uses a thin, electrically-conductive film applied to the surface of, for example, an airplane or a windshield or almost any other object in need of ice protection. The film is then heated with a milliseconds-long pulse of electricity. The beauty of this method is that only a micrometer-thin layer of ice directly at the ice-material interface is heated without having to heat the bulk of the object to which the ice is stuck. Even in extreme cold, PETD achieves nearly perfect efficiency because neither the object nor the air is heated—the heat simply does not have time to propagate into the environment. Just one single pulse of electricity melts the interfacial ice and instantly releases any additional build-up, which then easily slides off. Regular electric pulsing can keep surfaces consistently ice-free while maintaining low overall power consumption.
The de-icing film can consist of either a transparent conductor (such as indium tin oxide) for window or lens applications, or of a more durable coating (such as titanium) when extra wear-resistance is needed. For protection of large surfaces, thin metal foil or carbon-fiber composites are most effective.
Learn more about PETD:
The ability to quickly and efficiently release ice from any surface also has significant implications for refrigeration and ice making. This movie shows the de-icing of a residential icemaker equipped with PETD technology:
PETD provides up to a 90% reduction in energy use for residential ice makers, and up to a 40% reduction for commercial ice makers. The benefits of PETD are especially clear with commercial ice makers which consume enormous amounts of power as they cycle through a process of cooling to make the ice, and heating to release the ice as many as 100 times per day. PETD eliminates the need for the heating and re-cooling portion of the cycle, thus cutting energy consumption almost in half.
"The cost of electricity used in commercial icemaking is approximately $10 billion per year," says Petrenko. "Our technology can cut that number almost in half, by $4 billion, or approximately the entire annual budget of the National Science Foundation."
Several US and foreign companies are also adopting this technology to develop a "rapid evaporator defroster," which would significantly improve the overall efficiency of refrigerators.
Almost no heat energy is lost or wasted in this process and this optimal energy-efficiency in melting ice from surfaces is what makes PETD energetically feasible for aerospace applications and automobile windshields. Resistive heaters, such as the heated wires on rear windows of cars, cannot melt ice from windshields or wings because strong convective heat loss prevents the wires from reaching ice-melting temperatures without unrealistically high power usage.
This movie shows an aerofoil de-icing test in Dartmouth's icing wind-tunnel facility:
Goodrich Aerospace has completed the first in-flight testing of PETD on a small prop-plane. The results were "outstanding," and Goodrich is now developing a PETD system for large passenger airplanes.
De-icing of commercial buildings and bridges
Heat loss to the earth and air is the reason traditional heaters are impractical for de-icing roads, bridges, walkways, and roofs. But Petrenko's super-efficient PETD has demonstrated immediate effectiveness and saves up to 99% of electric energy compared to conventional heaters.
A de-icer for an over 100,000 square foot glass roof in Moscow, Russia was installed and successfully tested during the '09–'10 winter.
Petrenko's PETD method was also put to the test in Sweden where a 1712-meter-long "cable stayed" bridge is experiencing major problems with icing. The $250 million publicly-funded bridge currently must be closed down for significant periods of time during the winter months due to dangerous chunks of ice falling at random off the towers and cables from heights of up to 140 meters.
The first tests of PETD on a few cables and one pylon demonstrated instant de-icing action at very low energy consumption as compared with conventional de-icers.
Power Line De-icing
A more recent proprietary technology (different from PETD) is called a variable resistance cable (VRC) de-icing system. With only minor cable modifications plus some off-the-shelf electronics, the system switches the electrical resistance of a standard power line from low to high. The high resistance automatically creates heat to melt ice build-up or keep it from forming in the first place.
Co-invented by Dartmouth Engineering Professor Charles Sullivan, the VRC de-icing system was successfully installed and tested on a single distribution power line in central Russia, and full-scale installations in regions of Russia and China are now being planned.
The changes in manufacturing and installation required to implement the VRC system would result in a less than 10 percent increase in overall cost. Since utility companies normally replace 3 percent of their cables every year, the system could be installed as part of the regularly scheduled maintenance process and still achieve a significant portion of the installation by the time the next major storm hits.
Furthermore, the life span of the de-icing system would match or exceed the life-span of the utility cable, approximately 30–50 years. The system would pay for itself during the next storm by practically eliminating the cost of fixing downed cables and power outages due to ice and snow.
Another benefit to the VRC system is that utility companies using the system would have full control over its functionality. Time, temperature, and location can all be adjusted manually or set and controlled automatically with electronic sensors.
Overall, ice constitutes a major toll on society—airplanes downed, grounded, or rerouted, car accidents on icy bridges, power outages, ships capsized—so much so that it's difficult to quantify. "It's all very exciting and is keeping me very busy!" says Petrenko, "The Army Research Office (ARO) was the first to recognize that an investment in basic research was the place to start to solve this problem. Soon after, the National Science Foundation added its support, and that approach has worked very well!"
Cruise-control for your skis?
The same concept of applying short pulses of electricity directly to an ice-material interface can also be used to control whether ice is sticky or slippery. Electronic friction control for winter sports equipment—serving as electronic brakes or "electric wax"—is thus another application for Petrenko's ice-control technology
For skis equipped with a thin, electrically-conductive layer along the base, one pulse of electricity causes just a few microns of interfacial ice or snow to instantly melt and refreeze to the ski base—all within approximately 3 milliseconds (3/1000 of a second). This melting and refreezing forms a strong bond between ski and snow, increasing friction either to provide grip for kicking forward on Nordic skis, or to limit one's speed when going downhill.
With this technology, novice skiers (and snowboarders) can set a slow speed for learning, parents can have cruise-control for their kids, and cross-country and telemark skiers can finally be free from the unreliable performance of wax, "fish-scales," and climbing skins.
"Our system provides a skier with enormous gain in performance and convenience," says Petrenko. "With our electronics, a skier can get from three to four times stronger traction timed precisely with a kick-and-glide motion. He or she can forget about difficult and lengthy waxing procedures and not worry about choosing the right wax for a particular temperature or snow condition. Our system works well on any snow at any temperature below freezing."
The sticking effect is similar to what happens when a wet, warm tongue freezes and sticks instantly to a metal flagpole. The metal flagpole conducts heat away so quickly that the tongue freezes to it, even though it was warm an instant ago.
Since only one side of the interface needs high thermal conductivity, this system can also be adapted to car tires and shoe soles using electrically-conductive rubber which is already commercially available. Petrenko's team currently has a functioning shoe prototype that offers 40 times more traction on ice than a conventional lug sole. A tire-traction system that could eventually make snow tires obsolete is also in development.
"There's nothing like a 60-ton tank slithering around on the ice to make you think Professor Petrenko's technology is a good idea,"
—Herbert H. Dobbs, chairman of Torvec, Inc.
Winter Sports Competitive Advantage
- Up to four times increase in kick force
- No need for wax
- Reduces ski size requirement up to 50% for manufacturer
- Production cost savings through design flexibility
- Up to 40X better traction
- Production cost savings through design flexibility
Alpine and Snowboard
- Speed control through technology
- Braking system for snowboards
- Increased traction performance in varied conditions
- Reduces ski size requirement for manufacturer
The incredible range of applications for PETD is partly due to wide flexibility for electrode materials and configurations. For example, for aerospace PETD, Dr. Lev Deresh, an electrochemist on Petrenko's team, co-developed a practical process for manufacturing light yet durable electrically-conductive coatings, while another team member, Mikhail Starostin, Ph.D., made working prototypes for windshield PETD using transparent electrodes.
The list of applications for this technological breakthrough will almost certainly continue to expand. Stay tuned!